This invention relates to a system of alternately operating a plurality of disk players (hereinafter referred to as "a disk player alternate operation system", when applicable).
A system of alternately operating a plurality of disk players is well known in the art in which a plurality of disk players are selectively operated. The output is then reproduced by means of a single power amplifier, loudspeaker or a CRT (cathode ray tube). One example of a conventional disk player alternate operation system of this type will be described with reference to FIG. 1.
As shown in FIG. 1, in response to operation start signals from play control units 3 and 4, disk players 1 and 2 read audio data signals and video data signals from data recording disks such as DADs (digital audio disks) or video disks and demodulate them. The output signals of the disk players 1 and 2 are applied to respective input terminals of a switching unit 5. The output data signals of the disk players 1 and 2 are further applied to respective lead-out detecting circuits 6 and 7. Upon detection from the data signal of a lead-out signal indicating that the pickup has reached the lead-out area of the disk, each of the lead-out detecting circuits 6 and 7 outputs a lead-out detection signal which is applied to both the play control units 3 and 4.
The first play control unit 3 supplies an operation stopping signal to the first player 1 in response to the lead-out detection signal from the first lead-out detecting circuit 6 and, in response to the lead-out detection signal from the second lead-out detecting circuit 7, activates the first player 1 and simultaneously supplies a change-over instruction signal to cause the switching circuit 5 to select the data signal provided by the first player 1. Similarly, the second play control unit 4 supplies an operation stopping signal to the second player 2 in response to the lead-out detection signal from the second lead-out detecting circuit 7 and, in response to the lead-out detection signal from the first lead-out detecting circuit 6, activates the second player 2 and simultaneously supplies a change-over instruction signal to cause the switching circuit 5 to select the data signal outputted by the second player 2. The data signal thus selected by the switching circuit 5 is reproduced as a sound output or video output by a single signal reproducing system (not shown).
The operation of the disk player alternate operation system thus organized will be described in more detail.
When the operation instruction is made with the power switch of the system being turned on by the operator, the operation start signal is supplied to the first player 1 by the first play control unit 3 so that the first player 1 is operated. At the same time, the change-over instruction signal is supplied to the switching circuit 5 by the first play control unit 3, as a result of which the data signal provided by the first player 1 is supplied to the signal processing circuit thus being reproduced as an audio or video output.
On the other hand, the first player 1 reads data signals out of the data recording medium successively. When the first player 1 reads the last piece of music (the term "music" as used herein is intended to mean a single piece of music or a group of data including various events) and reads the lead-out signal indicating the end of the data, the first lead-out detecting circuit 6 detects it to provide the lead-out detection signal. In response to this lead-out detection signal, the second play control unit 4 supplies the operation start signal to the second player 2 to start it. At the same time, the second play control unit 4 supplies the change-over instruction signal to the switching unit 5 to apply the output data signal of the second player 2 to the signal processing circuit. On the other hand, in response to that lead-out detection signal, the first play control unit 1 applies the operation stopping signal to the first player 1 to stop it. That is, the first player 1 is placed in the initial state. When the operation of the first player 1 is ended in this manner, the second player 2 is started. Similarly, when the operation of the second player 2 is ended, the first player is activated.
In the above-described conventional system, the period of time which elapses from the time instant that the operation of one of the players is ended until the other player starts its operation is relatively long, as a result of which the condition that no sound or picture is reproduced lasts for a relatively long period of time whenever the operations of the players are switched over to each other.